Palladium Nanoparticles Supported on 4‐(Terpyridineyl)benzoic Acid/Zn‐Based MOF, as a Highly Efficient Catalyst for Selective Hydrogenation of C=C Bonds

ABSTRACT A fine Pd nanoparticles (NPs) were supported on a metal–organic framework (MOF) based on Zn(II) and 4‐([4,2′:6′,4″‐terpyridin]‐4′‐yl)benzoic acid (terpy) and 2‐aminoterephthalic acid ligands (terpy‐Zn MOF). Pd NPs were supported on the terpy‐Zn MOF by in situ reduction to Pd 2+ ions in the presence of terpy‐Zn MOF. Prepared Pd@terpy‐Zn MOF was characterized using scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDS), high‐resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) patterns, powder X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Barrett–Joyner–Halenda (BJH), and X‐ray photoelectron spectroscopy (XPS) analysis, and used as catalyst for the selective hydrogenation of C=C bonds. Pd@terpy‐Zn MOF exhibited high catalytic activity for the selective hydrogenation of C=C double bonds of α , β ‐unsaturated ketones and carboxylic acids, in which the C=O bonds remain unchanged. Pd@terpy‐Zn MOF‐catalyzed hydrogenation of chalcones occurred in 25%–93% conversion with excellent selectivity toward hydrogenation of the C=C bonds in the presence of the C=O bonds. Also, Pd@terpy‐Zn MOF efficiently catalyzed the hydrogenation of styrene derivatives to the corresponding ethylbenzene derivatives in up to 99% conversion. Aliphatic terminal and internal alkenes, such as 1‐decene and trans ‐2‐heptene, were also hydrogenated in the presence of Pd@terpy‐Zn MOF catalyst. The presence of hydroxyl, amine, and carboxylic acid functional groups in the structure of the alkene was well tolerated under the reaction conditions, to give the corresponding saturated counterpart in 94%–96% conversion. The study of the catalyst recovery indicated that the catalyst could be recycled and reused for five runs without a considerable loss in catalytic activity.